In a vehicle, backlash crossing may occur through the driveline when the wheel torque, or road load torque, and prime mover torque change direction from one another. The driveline may include the transmission gear system, driveline joints, and wheels. Lash, or backlash may occur for example due to lost motion caused by slack or clearance within various driveline components when torque changes direction, such as during a vehicle acceleration or deceleration event. Ignoring the effects of backlash crossing results in a disturbance for the driver.
In a conventional vehicle, a slow ramp on engine torque may be used when crossing the lash zone. Other methods to reduce the effect of lash crossing may also be used including spark retard within the engine, which may lead to reduced fuel efficiency and increased torque loading or oscillations on the engine that contribute to noise, vibration, and harshness (NVH). In a hybrid vehicle, controlling lash crossing in the driveline becomes more complex as there may be more than one prime mover providing torque to a single input shaft of the driveline. Detecting or predicting operating conditions or zones where driveline lash is likely to occur may be used to mitigate the effect of the lash crossing.